Automatic telephone system



* March 3l, 1931. G, RADKE V AUTOMATIC TELEPHONE SYSTEM 5 Sheets-Sheet l IIIIIJ &3 n S n R rimlmxlsllm Filed May 13, 19.29

EErZ-Lard Eadke March 31, 1931. G. RADKE AUTOMATIC TELEPHONE SYSTEM Filed May 13, 1929 5 Sheets-Sheet 2 QQ GY b ,sw 1M@ IE H H H 4 H s Q@ ESS E Nm\ @GN QJ. u L.

Mn N. nu Nm la@ BY Mm www Erl-15M Radke' March 31, 1931. G, RADKE 1,798,495

AUTOMATIC TELEPHONE SY'STEM Filed May 13. 1929 5 Sheets-Sheet 3 Earl-lard .Mairie 5 Sheets-Sheet 4 G. RADKE AUTOMATIC TELEPHONE SYSTEM Filed May 13, 1929 www@ ..| N ,mm mm March 3l, 1931.

fm Esi-Hard Eanlfs K AMG@ k# p kw March 31, 1931. G, RADKE 1,798,495

AUTOMATIC TELEPHONE SYSTEM Filed May 15, 1929 5 Sheets-Sheet 5 -Lmf l Earhard Essuie.

Patented Mar. 31, 1931 UNITED stares mans 'PATENT oFFiFE GERHARD RADKE, 0F BERLIN, GERMANY, ASSGNOR- T0 SIET/TENS L HALSKE AKTIEN- GESELLSCHAFT, OF WERNEBWERK, SIEMENSSTADT, NEAR BERLIN, GERMANY AUTOMATC TELEPHONE SYSTEM:

Application led May 13, 1929, Serial No. 362,509, and in Germany July 5, 1928.

In telephone systems kwith several exchanges and automatic working it is known that after a calling line hasj been connected to .a junction line outgoing in a particular 5 traiic direction it can be switched over to a Vjunction line outgoing in another traiic direction when the numerical selection has indicated that a connecting route is to be set up in the latter trailic direction. Now, the object or" the invention is to get the utmost use out of the switching devices that initiate Vthe switching-over of the calling line and to reduce as far as possible the number ot' these devices, in lsome cases even altogether avoiding the use of special switching devices. j y

`According to the invention, this is achieved in that a connecting device, which isv located in the calling subscribers exchange and in accordance with the number impulses transmitted connects a calling subscribers line with junction lines going in diilerent traffic direci tions, is controlled by switching devices Vwhich are located in different exchanges for example, in the calling sub-exchange UV t 1 and in the main exchange HVS 1) and are under the influence of the calling party.

i The circuits 1-7 show methods of carrying out the invention. Thus, Fig. 1 shows diagrammatically the arrangement of several exchanges.

In Fig. 2 is shown the call seeker AS, which can Abe reached by the subscriber Tnk 1 yin the sub-exchange UVS 1 shown in Fig. 41, and the preselector VW, which serves to switch over in the different tratc directions.

Fig. 3 shows a further portion of the connecting devices located in the sub-exchange UVSt 1.

Fig. 1 represents a further portion'of the connecting device located in the sub-exchange UVSt 1 and, in addition,itshowsthe main Y. exchange I-VSL 1, which can be reached over a two-wire junction line VL.

Fig. 5 shows a part ot the connecting de vices located inthe sub-exchange UVS 3 tsee Fig. .1). l

Figs. 6 and 7 show other forms of construction for the junction lines going to the main exchange HVSt 1 (three-wire junction lines). f

The rectangles enclosing the windings of certain of the relays, such as T, R, V, and'S ot' Fig. l indicate that these relays are made slow-acting by the addition or" a copper slug on the core of the relay or in any other manner well known in the art. f .i

By means of Fig. 1, a synopsis will first be given of the traffic-carrying devices accessible to the subscriber Tfn 1.

On taking down his receiver, the subscriber Tfn 1 over a call seeker AS and over a preselector VW in position 1 of the latter reaches a group selector GW 1 of the sub-exchange UVSt 1. It he wishes to reach a locall subscriber (for example, T122) of the same subexchange UVS 1, he will reach him over the group selectonGvW 1 and the final selector LW 1 of the sub-exchange UVSll. f

But, it he .wishes to reach a subscriber of another exchange, he will, by dialling a certain number for effecting a switching-over at y the group selector GW 1, ir'st move on the preselector V`W to the Contact 2 and so release the group selector GW 1 in the subexchange UVSt 1. This movingon causes the subscriber Tn 1 to seize a junction line of the main exchange HVS 1 over yan intermediate svvitch'Zl/Vand a repeater- Ue; and over that junction line he reaches a group selector GTV 4 in the ,main exchange HVS 1. The insertion of an intermediate switch'functioningasa non-numerical switch renders this junction line also available to incoming trunks from other sub-exchanges.v Inl accordance with the impulse train transmitted, the subscriber Tn 1 Awill now reach either a main exchange subscriber (for example, Tn 3) .over a group selector GW l and a final selector LW l in the mainexchange HVSt 1. or a j unctionf line going to another main exchange over af group selector GW 4 of'` the main exchange HVS?,L 1 standingon a certainlevel. Furthermore, by suitably operating a device (in Fig. 1an auxiliary switch MW) located in the main exchange HVSI 1,-

the subscriber Tn 1 can also make use of other connecting routes. Thus, if thetransmitted impulse train'be such that by means of the Y auxiliary switch MW the preselector VW in thesub-exchange UVSz-l bezmoved ontothe` Contact 3, the subscriberfTn 1 can release the connecting devices Which have been positioned in the main exchange HVSt 1, and can reach a subscriber for example, Ta l) of the sub-exchange UVS 3 over a group selector GWV 3 andl a final selectorLW 3 atV that sub=exchaiige UVS 3.

If, however, the transmitted impulse train Y be such that the preselector VW in the'sub- 4 exchange UVSt 1 be moved back to the conwill now be further explained with reference t te the other figures.

' to the preselector VWr and at Contact p it YWhen ai@ subseaberra i (Fig. 2) eases dovvn his receiver, the two-step relay T is energized over: learth, battery, resistance V172',

contact '1 t, subscriber Ta` 1, `Contact 2 t, Winding I of relay T,earth. The relay atl first only closes its contacts 3 t and 5 t. The

' closing of the Contact 5 t'eiiergizes the relay R over: earth, battery, relay R, contacts 4 p,

5 t, earth. The closing of the Contact 13 r e'nergizestlie rotary magnet D 1 of the'callV seeker AS over: earth, ielay interrupter RU 1, 'contacts 11 L, 12 t 1, 13 71, 14p, rotary niag-V net D 1, battery, earth. When the call seeker AS has found the calling subscriber, the following circuit is established: earth, contacts 26 fv, 24 r, windings I and'II of relay F, 'Wiper o 1 of call 'seeker AS, lead c, contact 375, Winding II of relay- T, battery, earth.

Relay P is operated iii this circuit 'and short circuits its high resistance Winding II at contact 25 p; by opening the contact 14- ,zo itV arrests the call 'seeker AS; at contacts' 19 p and 2O p it sivitches'tliroughthe leads a and Z) 'opens the energizing circuit of relay R. In

the circuit of rielayPthe Winding II of relay `T is alsor traversed by current; hence,`.this

relay noyvl operates'in its second step, so that the circuit for energizing the Winding I of relay T isy opened' 'at the contacts 1 25 and 2t.

The leads tl and having beenv switched through, therelay A is energized over: earth, battery, Winding I of relay A, contacts 22 t 1, 19 p, Wiper a 1 of the call seeker AS, lead a, subscriber Tfn. 1, lead Z9, Wiper b 1 of the call seeker AS, contacts 20 p, 28 t l, Winding Il of relay A, contact 31 s, earth. Thereby.

v p relay V is energized over: earth, contact 7 a,

relay V, battery, earth. Furthermore, the

over: earth, battery, rotarymagnet D 2, con- -devi'ce preselector VW is started up to hunt rowing to the `rotary magnet AD 2 being 'energized' tacts 60 s, 59 a, 58 t l, 57 L, relay interrupter RU 2, earth. n

The circuit oit' the tliermic relay TI-I is also closed at contacts 15o and 18a but this relay does not opera-te immediately. If no free junction line is available the circuit of the Vtheriiiic relay TH remains closed and 'after an interval this relay operates, and at its contact 56th closes an energizing circuit for VWindingI of relayS. VRelay S operates and at'it-s Contact 30.5 completesv locking circuit for itself over Winding II and transmits the busy tone to the calling subscriber over earth, bes., contact 30S, Winding II of relay A, contacts 28d, 20p, Wiper b1 of the call seeker AS, lead e of the subscribers line, subscribers station Tal, lead ci of the subscribersline, Wiper a1 of the call seeker AS, contacts 19p, 22H, Winding I Vof relay A,battery, earth. Relay S also opens the circuit of the rotary magnet D2 at contact 60s thereby stopping the preselector VV. in its hunting operation.

VJhen the preselector VIV finds a free j unction line,- for example the one having the leads a 3,y Z) 3;"0 3, (Z 3, e 3 going to the connecting' device shown in Fig. 3, al circuit is closed over: earth, battery, windings I and II of relay T 1, contacts 11 a, 39 s, 37 q, 35 (a, Wiper o2 of thev preselector VW, lead c 3,`thermic relay THjl, Winding I off-relay` C, vertical oil-normal contact 61176, rotary off-normal contact G5 w, earth. yThe relays 'I 1 and G are operated in this circuit. The opening of contact 58 t l arrests the preselector VW. A v

locking circuit'forrelay A and an energizing circuit fortlie relays I-I and Y are closed at contact 21 t 1 over: earth, Contact 21 t l, relay Y,`relay II, winding I of relay A, battery,

. earth. At contacts 23 t l and 29 t 1 thejunction line is switched through to the lleads a 3and b 3; hence the relay A 17(Fig. 3) is noiv venergized over.v` the subscribers -loopg Relay C havingbeen energized, the contact 67 c closes aflocking circuit for relay C and an energizing circuit for the relay VV 1 over:

earth, contact 67 c, Winding II of relay C,

Contact 69 a 1, relay kV 1, battery, earth; The closing'orcontact 66 o 1 connects the resist- -ance Wt in parallel Withrelay C tothe lead cv 3. Y

If the subscriber Tn 1 doesy not transmit any impulses Within a given time, the theriiiic relay 'Iz, 1 isoperated over the above- Vdescribed circu for energizing the relays T 1 and C; hence the contact 62 157@ 1 is closed" andl thereby the relay Sv is energized over:

Winding I of relay S, battery, earth. At contact 39 e' is opened the circuitfor energizing therelays C and T l; hence the connecting (Fig. 3) seized in the sub=exchange "UVS 'l is released Vand the subscriber Ta 1 receives the* busy signal over z earth, bes.,con tact 308, Winding II of relay A, contacts'28 t 1',

20 p, wiper?) 1 of the call seeker AS, lead b,

subscriber Tn 1, lead a, Wipera 1 of the call seeker AS, contacts 19 p, 22 t 1, winding I of relay A, battery, earth. During this time the relay S locks itself over: earth, battery,-

nets of a connecting device, such as GIVI,

which is partly shown in Fig. 3 and is located in the sub-exchange UVStl and selects a desired route. If the group selector GVI is operated to the first level or any other level assigned to local subscribers, an idle final connector, such as LVl, is seized and the dialling of two additional digits connects the calling subscriber to a subscriber in the same sub-exchange UVStl. In the example shown, the tenth level is used to designate an outgoing call while the second level is used for trunks to the sub-exchange UVSt2. The remaining levels may be used for local traiiic. Thus if the digits 1, 2 and 3 were dialled the calling subscriber would be connected to subscriber Tf/L2 of the same sub-exchange UVStl.

But, if the subscriber Tal wants a sub-Y scriber of some other exchange, he must first dial a designating digit. In our example it is assumed that this is the digit 0. Therefore,

,if the. subscriber transmits 10 impulses, the

switch GVVI which is located in the sub-eX- change UVSI, is raised to the tenth level. IVhen this has been reached, the level contact 63k@ is mechanically operated so that the following circuit is established: earth, contacts 61o2, 637m, lead e3, wiper e2 of the preselector VIV, contacts 49m, 48h, 43m, 42g, winding II of relay U, battery, earth. Relay V2 was energized at the first interruption at the bef ginning of the impulse train over: earth, contacts 670, 68a1, relay V2, relay V1, battery, earth; but restored to normal a short time after the cessation of theinipulse train. Relay U locks itself over: earth, battery, winding II of relay U, contacts 42g, 43m, 46u-, 52s, 53o, earth. The contacts 35u and 36u open the circuit forl energizing the relay T1 and prepare the test circuit over the wiper cl2 of the preselector V W. After the release of relay T1, the relays H and Y .also fall back; hence the rotary magnet D2 of the preselector VW is energized over: earth, battery, rotary magnet D2, contacts s, 59a, 58H, 577i, relay interrupter RU2, earth; and the preselector VIV is moved on the hunt for a unction going t0 the main exchange I-IV S251 over a repeater Ue. Furthermore, after the preselector VIV has moved on, the relay A1 3) falls back; hence the short circuiting of winding II of relay C at contact 68a1 causes this ref Y lay to fall back also, and at contact 670 it opens the circuit for energizing the relay V1.

Contacts ofv this relay can then in some manner bring about the release of the positioned switch (not shown). After the release of relay Y Fig. 2) the relay X is energized over: earth, battery, relay X, contacts 451g, 46u, 52s, 53o, earth, and it later on locks itself over its contact 44m.

IVhen the perselector VIV has found an idle junction line (a 4, b 4, c 4, Z 4) over which can be reached the main exchange HVS 1, the following circuit is established: earth, contacts 86 a 3, 88 v 5, 84 h 1, 85 L 2, lead Z 4, wiper d 2 of the perselector VW, winding I of relay U, contacts 36 u, 37 g. 39 s, 41 a, windings I and II of relay T 1,. battery, earth. In this circuit is operated the relay T 1, and after relay A 3 has been energized over the speaking loop by the switching' through at the contacts 23 t 1 and 29 25v 1, the relay C 2 is also operated, which till now has been short circuited over contact 86 a 3. Therefore, after relay T l has been energized, the preselector is arrested and the relays I-I and Y are energized in the manner already described. The before-mentioned energizing of the relay A 3 takes place over: earth, battery, relay A 3, lead a4, Wiper a 2 of preselector VWr, contacts 23 t 1,19 29, wiper a 1 of the call seeker AS, lead a, subscriber Tn 1, lead wiper' Z) 1 of the call 'seeker AS, contacts 20 p, 29 1, wiper b 2 of preselector Vl/V, lead o 4, choke coil Dr 3, earth. Relay f C 2 having been energized, the relay V 5 is energized over earth, Contact 89 c 2, winding II of relay C 2, contact 91 a 3, relay V 5,

battery, earth. At contact 87 o' 5 (make before break) is closed a locking circuit for relay T 1 over the resistance W2'. After its winding I has been disconnected, the relay C 2 locks itself over winding II in the previous` ly described circuit for energizing relay V 5.

By transmitting further trains of impulses the driving magnets of the not shown switches (Fig. 1, GIV 4 and LW 4) can be operated to position the latter in the mail? exchange HVSI 1. This takes placeas follows: l

Vhen relay` A 3 is operated and before relay V 5 has been energized, the closing of contact 97 a 3 energizes the relay C 3 in the main exchange IIVS 1 (Fig. 4) over: earth, contacts 98 o 5, 97 a 3, 100 o7, lead Z) 6, contact v 10, off-normal contact 106 7c 3 of group selector GIV 4, contact 108 u 8,

relay C 3, battery, earth. The closing of contransmitted by the subscriber cause the relay A 3 to fall back in known manner at each impulse; hence in the main exchange HVS 1 the relay VA14 is energized at each impulse over: earth, contacts 104 c 2, 102 a 3, lead a 6 of the junction line VL, relay A 4, battery, earth. The irst time relay A 4 energizes, its contact 119 a 4 opens the short circuit, so that the relay V 9is energized over: earth,contacts 117 o 8, 118 s 1, relay V 9, relay V 8, battery, earth. Similarly, the removal of a short circuit (contact 91 a 3) in the sub-exchange UVSI 1 causes relay V 6 to be energized` over: earth, contacts 89 o 2,

90 a 3, relay V 6, relay V 5, battery, earth.V

Both relays remain energized forfthe duration of the impulse train, and only fall back after the impulses have ceased owing to the short circuit over the contact 119e 4 and 91 a 3. While these relays are energized, the relays V 7 (earth, contact 92 o 6, relay V 7, battery, earth) and V 10 (earth, contact 114 o 9, relay V 10, battery, earth) are enen gized. The group selector GTV 4 can then be positioned onto the wanted junction line by means of impulses received 'by the relay f A 4 in the main exchange.

For example, if the transmitted impulse train does not consist of 3, 4, 7 or 8 impulses, the group selector GWV 4 in known manner will test thejunction line reached over arm c 7 owing to relay P 1 being connected up over: earth, contact 113 o 8, windings I and l1 of relayP 1. lf the line be free, the relay l) 1 is energized in known manner and the junction line VL is switched through to the junction line seized by the group selector i n ow i.

yThe modification using level contacts on the selector switch G1174 will first be described. ln this case the lead o6 of the junction line VL is connected to the level contacts 7678 and M14, that is, the points 1 and 2 are permanently connected.

1f the first impulse train received at the main exchange HVStl consists of three or four impulses, the level contact 34'of the group selector GvV 4 is mechanically operated when tlie third or fourth level is reached. Thereby the following circuit is established: earth, battery, resistance VVz', level Contact 34 of the group selector GW 4, contact connection 1, 2, lead Z) 6 of the junction line VL, contact 101 o 7, windings l of therelays H 1 and H 2, earth. Owing tothe insertion of the resistance vVz' in this circuit, only the relay H 1 is operated, and at the end of the im pulse train this circuit is again disconnected at the Contact 101 o 7, because, as previously mentioned, at the end of the impulse train the relay V 6 isreleased andby opening its contact 92 o 6 it also causes the release of the relay V 7. Before the windings T of the relays H 1 and H 2 have been disconnected, the relay H 1 closes a locking circuit for itself over: earth, contacts 94 c 2, 93 h 1, winding I1 of relay H 1, battery, earth. By closing the vcontact 82 7L 1 the relay Q (Fig. 2) is energized over: earth, battery, winding I of relay Q, contacts 33 h, 34 Wiper c 2 of the preselector' VTV, lead 0.4, contacts '82 'It 1, 83 7L 2, earth. Relay Q locks itself over its Contact 8 q in the circuit: earth, contacts 7 a, 8 g, winding 1I of relay Q, battery, earth. Contact 37 g opens the test circuit extending over wiper l 2 of the preselector, while the closing of Contact 38 g prepares a test circuit over wiper e 2 'of the preselector. Further-more, the opening of contact 37 g releases relay T 1; hence the rotary magnet D 2 of preselector VW is energized over: earth, battery, rotary magnet D 2 of preselector VlV, contact s 59 a, 58 t 1, 57 k, relay interruptei` RU 2, earth, after relays H and Y have been released by the opening of contact 21 t 1.- 1n additiointhe opening of contact 42 g releases relay U and then the opening of contact 46 u releases relay X. The preselector VYVV is moved on; hence, first the relay A 3 (Fig. 4) falls back and at contact 90 a 3 it short circuits the relay C 2 Which opens its contacts 89 c 2 and 94 c 2. Thereby the relays V 5 and H 1 are also released.

At the time the level contact 34 of the group selector GWV 4 Closes the circuit of the relay H 1, it also closes a circuit for relay S 1 over: earth, battery, resistance WZ', level contact-'itI l34, Contact connection 1-2, contact 105 'v 10, 0H-normal contact 107 k 3. winding I of relay S1, earth. Relay S l closes a locking circ-uit for its winding II over: earth, contacts 115 s l, 116 o 8, winding II of relay S 1, battery, earth. At the same time it opens the circuit of `relay V 8 at contact 118 s 1 and short circuits relay P 1 at contact 109 s 1, thereby bringing about the release of the group selector GW 4. The locking circuit of relay S 1 is opened at contact 116 'v 8 by the release of relay V 8.

Vithf its wiper e 2 the preselector VW tests a. free junction line going to the subexchange UVS 3 shown 'in the Fig. 5. Vhen it finds such a line (Fig. 5, a5, b5, e5), a circuit is closed over: earth, battery, windings I and H of relayT 1, contacts 41 a, 39 8, 38 g, wiper e 2 of preselector VW, lead e 5, winding I of relay C 1, off-normal contact 76 c 1,1-0- tary off-normal contact 7 7 w 1,earth. Therelays T 1 and C 1 are energized in this circuit. The opening of contact 58 t 1 arrests the pre-y selector VV\ and the closing of contact 21 t 1 energizes the relays H and Y. At contacts 23 t 1 and 29 t 1 the junction line is switched through tothe leads a 5 and Z) 5; hence the relay A 2is energized over the subscribers loop. The lclosing of contact 79 cv 1 establishes a circuit for locking relay C 1 and for energizing relay V 3 over: earth, contact 79 o 1, winding II of relay C 1, contact 81 a 2, relay V 3, battery, earth. The closing of con tact 78 c 3 connects a shunt circuit to the lead e 5 over the resistance We'. mitting further impulse trains (2, 2, 1) the subscriber Tn 1 can then reach the wanted subscriber (e. g. Tn 4) of the sub-exchange.

If the impulse train transmitted after preselector VlV has been set on the connectingl device of the main exchange HVSt 1 cornprises 7 or 8 impulses Vinstead of 3 or 4 impulses, th'e level contact 70 78 is mechanically operated by the group selector GIV 4 at the end of the impulse train. The following circuit is established: earth, battery, level contact c 78, contact connection 1, 2, lead 6 of the junction line VL, contact 101 'v 7, windings I of relays H 1 and H 2, earth. Relays` H 1 and H 2 are operated in this circuit and lock themselves over: earth, contacts 94 c 2, 93h 1, winding II of relay H 1, battery, earth', and over earth, contacts 94 c 2, 95 h 2, winding II of relay H 2, battery, earth. At the same time at contact Z0 7 8 the relay S 1 is energizedover: earth, battery, level contact ,7c 78, contact connection 1, 2, contact 105 o 10, eff-normal contact 107 7c 3 of group selector GIV 4, winding I of relay S 1, earth. The energizing ofrelay S 1 is followed by the release ofthe connecting devices inthe main exchange HVSt 1 in the manner already described.

The energizing of the relays H1 and H 2 causes the test circuit extending over the Wiper Z 2 of preselector VW to be opened and thus is interrupted the circuit of the relays T 1 Aand U. The closing of contact 35 uv prepares a test circuit over wiper c 2 of pre-` selector After relay T 1 has fallen back, the rotary magnet I) 2 ofpreselector VW is energized over: earth, battery, rotary magnet I) 2, contacts s, 59 a, 58 t 1, 57 h,

relay interrupter RU 2,- earth, after relaysl Hand Y have been released bythe opening of contact 21 t 1. Preselector V VV is moved 45 on and relay A 3 (Fig. 4) falls back. Thel short circuiting of winding II' of relay C, 2 atcontact 90 a 3 causes thisrelay to fall back and at contact 89 c2 to open the circuit of relay -V 5. -In addition, the locking circuits of relays H 1. and H 2 are opened at Contact 94 c 2.

Over its wiper c 2 the preselector VW now tests for a free connecting device in the .same sub-exchangeUVS 1. This connecting device (GW 1) may be the same as that previously referred to for setting up a. connection to a subscriber of the same sub-exchange;,

namely, leads a 3. b 3, c 3, d 3, e 3 and the group selector GW `1.

The setting up of the connection nowtakes place in the manner already described. The

subscriber Tn 1, by dialling (digit 2)', sets the connecting device 1, GW 1) onto 'a Contact, to which is connected ajunction line going to the .sub-exchange UVSt 2. By transmitting further impulse trains (digits By trans- 2, 2, 1) and thus positioning the connecting'V devices (GWV 2 and LIV 2 in Fig. 1) 'in thei sub-exchangeUVSt 2, the subscriber can thenl reach the subscriber Tn 5 (Fig. 1) -of the sub-exchange UVSt 2.

Upon the release of the connection, the call seeker AS and preselector VW are released Y y and A. The opening of contact 27 a releases 1 the relays P and T, 'and the opening of con- 'l Y tact 7 a releases the Vrelay V. Thus, the call seeker AS and preselector VW are rendered free for another'call.

so"a

Instead of effecting the switching over into the various traflic directions by actuating different level contacts (lo 34, lo 78), it is pos-1 sible to do it by means of an auxiliary switch MW as shown in Fig.l 4. In that case, the'contact connection between the points 1 and 2 is replaced by a connection between the points 1 and 2. This arrangement then operates inV een" tact 123 w 3, contact 125 'v 8, earth, in vaccordance with the'transmitted impulses.

If the transmitted impulse train comprises 3 or 4 impulses, the wiper d' 31 of the auxiliary switch is positioned onto the thirdLor A fourth contact. Hence, when relay 9 is released atl the end ofthe impulse train, a circuit for energizing 'the relay H 1 is establishedV over: earth, battery, .contacts 127 fu 8, 126 c 9, wiper al 31 of theV Wt y f tion line VL,`cont-act 101 v 7, winding I of relay I-I 1 and of relay H 2, earth. As y auxiliary switch MW, resistance contact terminals 2', 1, lead b 6 of juncpreviously mentioned, the resistance We' pre- "vents the relay H 2 being operated. Therefore, the closing ofthe contact'82 h 1 effects the switching over of the preselector VW to the sub-exchangeyUVSt 3, as already described.

If the impulse train `comprises 7 or 8'imy pulses, the wiper d 31 of the auxiliary switch MW stands on the' contact or'8 at the end of the impulse train; hence, over the lead b 6 a circuit is Vnow established in which the relays kH 1 and H 2 are operated. The opening ofV the contacts 84 7L 1 and 85 h 2 then causes the previouslyv described return to a connecting device in the sub-exchange UVSZ 1.

Instead of using a two-wire junction line VL (a 6, b 6), it is possible to use three-wire with Figs-6 and 7. The circuit changes taking place are the same as those .described above. In the Fig. 6 the relay C 3 is energized in the same manner as in Fig. 4, except that its circuit extends over a third lead c6 instead of over the lead b `6 of the junction line VL.

In the Fig. ,7 the third lead c 6 of the junction line VL is used lfor controlling the relays H l and H 2 in accordance with the transmitted impulse train. l

We have seen that every subscriber who wants to speak to a subscriber of another exchange has to dial a particular number (.0). Thereby in accordance with the example a simplilication of the the telephone directory is etl'ected as regards numbering, .and `in addition the .unnecessary seizing .of the heavily loaded outgoing lines to the main exchange is avoided when the subscriber wants a sub scriber ot' the same exchange.

What is .claimed is: Y

1.. In a telephone system, .an automatic switch, three groups ot trunks accessible to said switch, means for operating said switch .to select a .trunk in one group, `and means rcsponsive to a digit transmitted over the sclected trunk `tor reoperat'ing sai-d vswitch to select a trunk in the second or third group depending on the value of the digit.

2. In a telephone system, an automatic switch, means for operating said switch te select a second switch, means controlled from the second switch for causing the tirst switch to `select a third switch, and means controlled trom said third switch for causing said lirst switch to select a fourth switch.

3. In a telephone system., two sub-e. changes anda main exchange, a non-numericalhunting switch in the vfirst sub-exchange, numerical switch accessible to said hunting switch, local trunks and trunlrs to the second sub-exchange accessible to `said numerical switch, nand trunks to the main exchange ac ces'sible to said non-numerical hunting switch.

4. In a telephone system, three sub-exchanges and a main exchange, a non-numerical hunting switch in the first sub-exchange, a numerical switch accessible to said huntingswitch, local trunk-s and trunks to the second .sub-exchange accessible to said numerical switch, and two groups of trunks extending to the third sub-exchange and to the `main exchange, respectively, accessible to said hunting switch.

5. In a telephone system, a main exchange and a number of sub-exchanges. a non-numerical hunting switch in the iirst sub-exchange, means responsive to the lseizure otsaid switchy tor operating same tev select one eta group ot local trunks, means responsive to a digit dialled and dependent-'upon the value of the digit for reoperating said switch to select one ot a group of trunks to the main exchange, and means responsive to the suc- Seeding digit dialled, providing said digit indicates a diii'erent tra-hic direction, for releasing saidmain @Hice .trunk and reoperating said switch to select the proper trailic direc tion.

6.7Ina telephone system, a sub-exchange including a non-numericalhunting switch, a trunk extending to a main exchange,'tw0 re lays in the trunk at the sub-exchange con.- trolled over one lconductor of .said trunk, means for operating .said hunting switch to selectsaid trunk, means in the main exchange responsive to a -digit dialled for returning a signaling current to operate the first .of said relays to indicate a particular traffic .directionI and means in the main exchange responsive to va ldifferent .digit ,dialled for returning a different signaling current to .operate loot-hoiV said rela-ys to indicate .another trattic vdirection.

7. In a telephone system, a plurality of sub-exchanges .and .a main exchange, a nonnumerical hunting switch in the tirst of .said sub-exchanges., a numerical .switch accessible to said hunting switch, means `controlled from said numerical .switch responsive to a digit dialled and vdepending on ,the value of said digit for causing .said hunting switch to select one of a group of trunks to the main exchange,

two relays in said trunk at the sub-exchang means in the main exchange responsive to the succeeding digit dia-Hed and depending en the value et said digit for returning a signaling current .over said trunk to operate the First of said relays to indicate a particular trafiic Y direction, and means responsive to a different digit dialled and depending on the value of said digit for returning a .different signaling' current .over saidtrunk line to operate both of said relays to indicate a different traiiic direction. y

8. In a telephone system, an exchange including two automatic switches, a trunk line extending to a second exchange and termin ating in an automatic switch, means responsive to the seizure of the rst of said switches for seizing the second of said switches, means responsive to the operation of said second switch to a predetermined position for releasing same and for reoperating said first switch to seize said trunk line, means responsive to the operation of said switch in said second exchange over said trunk line to a predetermined position for releasing same and Y having a dial, means responsive to the re# moval ot the receiver at said stationfor seizing said Vswitch and for operating same to a first position, means responsive to the operation of said dial and dependent upon the digit i dialled for causing said switch yto operate to a second position, and means responsive to the succeeding operation of the dial and dependent upon the next digit dialled for causing said switch to again operate to said first position.

10. In a telephone system, an exchange including two automatic switches and a station equipped with a dial, a trunk line extending to a second exchange, a second trunk line extending to a third exchange, means responsive to the removal of the receiver at said station for causing said irst switch to seize said second switch, means responsive to the operation of said second switch by said dial and dependent upon the digit dialled for releasing same and causing said first switch to reoperate to seize said iirst trunk line, and means in said second exchange responsive to the succeeding operation of said dial and dependent upon the digit dialled for causing said first switch to reoperate to either seize said second trunk line or again seize said second switch.

11. In a telephone system, a non-numerical hunting switch having access to three groups of trunks, means responsive to the seizure of said switch for operating same to select an idle trunk in the iirst of said groups, means responsive to a predetermined digit transmitted over the selected trunk for reoperating said switch to select an idle trunk in the "econd of said groups, and means responsive to a predetermined digit transmitted over said second selecte-d trunk for reoperating said switch to select an idle trunk in the third of said groups.

12. In a telephone system, a non-numerical hunting switch having access to threee groups of trunks, means responsive to the seizure of said switch for operating same to select an idle trunk in the iirst of said groups, means responsive to a predetermined digit transmitted over the selected trunk for reoperating said switch to select an idle trunk in the second of said groups, and means responsive to a digit transmitted over said second selected trunk and dependent on the value thereof Jfor reoperating said switch toeither select an indle trunk in the `third of said groups or again select an idle trunk in said first group. Y

13. In a telephone system, an exchange having local trunks and trunks extending to a second exchange, a subscrihers station equipped with a dial in said rst exchange, means responsive to the removal of the re- ^eiver at said station for extending a connection to one of said local trunks, and means responsive to the dialling of a particular digit for releasing said local trunk and extending a connection to one of the trunks to said secl`nd exchange.

14. In a telephone system, an exchange having local trunks and trunks extending to a second and a third exchange, a subscrihers station equipped with a dial in` said irst exchange, means responsive to the removal of the receiver at said station for extending a connection to one of said local trunks, means responsive to the dialling of a particular digit for releasing said local trunk andextending a connection to one of the trunks to said second exchange, and means responsive to the dialling of a succeeding digit of predetermined value for releasing the trunk to the second exchange and extending a connection to one of the trunks to said third exchange.

15. In a telephone system, an exchange having local trunks and trunks extending Vto a second exchange, a subscribers station in said lirst exchange equipped with a dial, means responsive to the removal of the receiver at said station for extending a connection to one of said local trunks, means responsive to the dialling of a predetermined digit for releasing said local trunk and extending a connection to one of the trunks to said sec.- ond exchange, and means responsive to the dialling of another digit of predetermined value for releasing the trunk to the second exchange and again extending a connection to one of said local trunks.

16. In a telephone system, three exchanges, a non-numerical hunting switch and a numerical switch in the first exchange, trunks to the second exchange accessible to said numerical switch, trunks to the third exchange accessible to said hunting switch, and means responsive to the seizure of said hunting switch 'for operating same to seize said numericalswitch.

In witness whereof, I hereunto subscribe my name this 19th day of April, A. D. 1929.

GERHARD RADKE. 

